Re: question on page-migration code

Ray Bryant
2005-04-11T19:59:35Z

Marcello,

Checking /proc/vmstat/pgpgout appears to indicate that the pages I am
migrating are being swapped out when I see the migration slow down,
although something is fishy with pgpgout. pgpgout is supposed to be
KB of page I/O, but I know that I am migrating 8685 pages, at 16KB/page,
or 138960 KB. pgpgout gets incremented by roughly twice this.
So it looks like either:

(1) pgpgout is really sectors written, or
(2) pages are being paged out twice as part of memory migration.

I still don't understand why this pageout process doesn't happen
every time I do a migration (e. g. never on the first time),
and why it is taking 210 s to page out 138960 K. That's around 600 KB/s
of I/O to the paging disk.
--
Best Regards,
Ray